1. Technical Field
The present invention relates to a device for controlling current of a light emitting diode (LED), and more particularly, to a device for changing current of an LED capable of changing current determining brightness of the LED without separately changing an external power supply or a resistor.
2. Description of the Related Art
An organic light emitting diode (LED) has been widely used in various fields such as illumination, a backlight unit (BLU), or the like. Recently, as a market for the LED has rapidly expanded, the related technologies have rapidly advanced correspondingly.
Meanwhile, the current of the LED are mainly set and controlled by a conversion dimming signal (ADIM) and a resistor (RLED) parameter. When voltage is applied from the outside, a noise included in the voltage appears in output current as it is. Therefore, a scheme of changing an external resistor has been mainly used.
However, even in the case of using the scheme of changing the external resistor as described above, since a resistor of each of the LED modules should be changed, it is difficult to standardize the LED modules.
FIG. 1 shows an LED driving circuit most widely used in the related art.
As shown in FIG. 1, a constant current generator 110 generates reference current (Iref) to LED current (ILED) using ADIM voltage and an RLED and transfers the reference current to an input end 131 of a current amplifier 130 using a current mirror 120, and the current amplifier 130 may obtain the LED current (ILED) corresponding to N times of the reference current using the ratio (N:1) of a resistor A to a resistor B.
Herein, in order to change the LED current (ILED), the ADIM voltage or the RLED should be changed. However, as described above, when the ADIM voltage is input from the outside, an input noise may be reflected on an output as it is, and when the RLED is changed, it is difficult to standardize the LED module.
In addition, in order to change the LED current, a single wire control scheme, a single wire clock counting scheme, and the like, in which a separate digital block is added may also be used. However, in the case of using the digital block, a separate digital source for generating a complicated digital clock signal is required.